cvs only kernel source

What would a cvs co for the kernel sources only look like?
I tried 'cvs co -P -r netbsd-5.0.2 sys' but got a "no such module" error messge.
Best regards,
--
No no no, my fish's name is Eric, Eric the fish. He's an halibut. I am
not a looney! Why should I be tarred with the epithet looney merely
because I have a pet halibut?